Reinforced plastic structures



Sept. 9, 1958 .J. F. LEAHY ETAL 2,850,752

REINFORCED PLASTIC STRUCTURES Fild Sept. 7, i956 2 Sheets-Shegt 1 Inventors 26' RobertlLPelletz'er James E Leah y II I Y .59 their Aftorrzey p 9, 1953 J. F. LEAHY EFAL 2 ,850,752

REINFORCED PLASTIC STRUCTURES Filed Sept. 7, 1956 2 Sheets-Sheet 2 Inventors Poberi Pellefzer James F Leaky By zlzez'rA flomey United States Patent REINFORCED PLASTIC STRUCTURES James F. Leahy, Beverly, Mass., and Robert I. Pelletier,

Moundsville, W. Va., assignors to United Shoe Machinery Corporation, Flemington, N. J., and Boston, Mass., a corporation of New Jersey Application September 7, 1956, Serial No. 608,524

3 Claims. (Cl. 12-136) This invention relates to light, strong plastic structures and particularly to an internally reinforced plastic last heel end.

In the making of shoes the parts of the shoe upper are disposed on a last and are shaped and combined with other shoe parts while on the last. The frequent handling of the shoe and last in the course of shoe manufacture makes it imperative that the last he as light in weight as possible consistent with having the necessary strength to withstand the stresses imposed on it. Wood lasts, particularly rock maple wood lasts, have been used almost universally for a substantial period. New shoemaking machines and processes are being and have been developed in which the machinery performs automatically operations which heretofore have required the exercise of judgment on the part of skilled craftsmen. These new machines require that the last meet new standards of dimensional stability in order to function properly. Also, in some cases the new machines apply greater loads to the last. Even rock maple wood has not proved fully satisfactory from the standpoint of strength; and changes in humidity conditions may change the dimensions of a last almost a full size.

Resinous compositions have been tried as materials for lasts. In general, lasts made of these resinous compositions have either been too heavy, too expensive, or have been lacking in strength or dimensional stability. Metallic inserts have been tried as reinforcements for lasts of resinous material;v but these inserts have not cooperated well with the resinous body of the last. In some measure this is due to the different coefficients of thermal expansion between the resinous material and the metallic insert. Also the sharp dilference in mechanical strength and flexibility between the metallic insert and the resinous body of the last causes localized stress at the boundaries between the resin and metal.

It is a feature of the present invention to provide a new, light, strong, dimensionally stable, reinforced resin structure having reduced stress localizing boundaries between. the reinforcement and the main body of the material.

It is a further feature to provide a light, strong, dimensionally stable last heel end including this new reinforced resin structure.

These and other features are described below and are illustrated in the accompanying drawings, in which,

Fig. 1 is an angular view of a last heel end according to the present invention and with a last forepart shown in phantom;

Fig. 2 is a cross sectional view of a last heel end according to the present invention, taken on the line II--II of Fig. l; g

Fig. 3 is a cross sectional view of the last heel end of Fig. 1 taken on line IIIIII;

Fig. 4 is an angular view of a reinforcement portion for a last heel end and of the mold parts forforming it;

Fig. 5 is a cross sectional view of a reinforcement portion takenon line VV of Fig. 4;

Fig. 6 is an angular view of the mold parts for forming a last heel end showing a molded reinforcement portion in one of the mold parts; and

Fig. 7 is an angular view of another pattern of reinforcement.

According to the present invention there is provided a structure comprising a continuous phase of. strong, preferably thermoset resin extending substantially throughout the structure. A reinforcement for the structure is provided by disposing solid particles of reinforcing inorganic filler material in portions of the continuous phase. The portions containing the inorganic reinforcing filler are stronger but heavier than the remaining portions of the structure. The volume and shape of such portions may be arranged to give maximum strength and lightness as for example in an I cross section.

The remaining portion of the continuous resin phase may be filled with uniformly dispersed hollow resin spheres to give desirable over-all lightness to the entire structure.

In a last heel end, according to the present invention, the reinforcement portion may comprise an inorganic filler loaded resinous portion surrounding the openings for the last hinge pin and a portion of beam-like outline extending substantially from top to bottom of the last heel end, these portions being linked together.

The new structure will be described in connection with a last heel end constituting an important embodiment. It will be understood that the structure is useful in other relationships where strength and light weight. are important.

A last heel end v10 (see Fig. 1) is a shaped piece which with the last forepart 12 makes up the complete last. The heel end 10 and forepart 12 are connected together by a hinge structure such as the complementary cylindrical bearing portions 14 shown in the figure and a hinge link (not shown) fitting in slots 16 in the last parts. When the heel end and forepart are in the position shown they form a last for making a shoe and when they are moved relatively about the hinge the last is shortened to permit its removal from a shoe. A last jack pin hole 18 is provided at the upper part of the last heel end to receive a last jack pin to hold the last in position in various shoemaking machines.

The last heel end 10 of the present invention provides a continuous body of resin (see Figs. 2 and 3) extending throughout the entire volume of the last heel end. Within the body of resin there is provided a mass 20 of inorganic reinforcing filler localized in a pattern providing the equivalent of a reinforcing beam but not interrupting the continuity of the resin phase. As shown in Figs. 2, 3, 4 and 5, the reinforcing filled portion 21 comprises a web portion 22 extending from the top to the bottom of the last heel end and extending forward to reinforce the last hinge pin holes 23. At the upper and lower edges of this web portion 22 there are provided laterally extending flange portions 24 cooperating with the web portion 22 to provide the equivalent of an I-beam. At the forward part of the reinforcing pattern the reinforcing forms a bifurcated section 26 providing a slot 16 for the hinge link and extending around the last hinge pin holes 23 to provide. a firm unyielding support fixing the last hinge pin holes in unvarying relation to the remainder of the last heel end. A reinforcing filler-containing flange shaped portion 28 also extends between the upper and lower flanges 24 of the I-beam section to provide additional load bearing capacity. The last jack pin hole 18 extends down into the reinforcement.

Other patterns of distribution of the mass of inorganic reinforcing filler may be used. It is important to provide a central portion of sufficient thickness to resist crushing under compression to which the structure may be subjected in use. It is also desirable to provide flanges or other shapes of increased thickness spaced from the neutral axis of the reinforcement portion in order to make most effective use of the reinforcing material.

The portion 29 of resinous material surrounding the portions 21 of the last heel end carrying inorganic reinforcing filler may be filled with a material which will reduce the over-all weight of the structure. A preferred filler material is the microscopic hollow resin sphere material commercially available as Microballoons and comprising hollow spheres of phenol-aldehyde or ureaaldehyde thermoset resin. The hollow resin sphere filled portions 29 of the last heel end structure possess substantial strength and resistance to compression to withstand the pressures of shaping a shoe upper but this strength is not adequate alone to absorb the loads applied to a heel end in such processes as heeling or sole molding, etc. A particularly advantageous factor, however, is that the resin continuous phase extends throughout the last heel end so that there is no excessive concentration of stresses between the inorganic reinforcing filler-containing portion and the hollow resin sphere-containing portion of the structure.

An alternative reinforcement pattern shown in Fig. 7 provides a reinforcing filled portion 21 having the same thickness from top to bottom and includes a' bifurcated section 26 providing a slot 16 for the hinge link and extending around last hinge pin holes 23'." In a last heel end (not shown) employing this reinforcement portion, as in the last heel end previously described, the continuous phase of resin extends through both the reinforcement portion and the remainder of "the last heel end and is particularly important to' protect' fag ainst splitting.

Various methods may be employed for forming the structure containing the two types of filler materials. According to one method a mixture of thermosettiiig' resin and inorganic reinforcing filler materialmay be" cast or molded to the desired shape of the reinforcing portion 21 and this precast reinforcement positioned in a last heel end mold, and the space surrounding the reinforcement 21 filled with amixture of thermosetting resin and hollow resin spheres. On curing this last resin mixture the thermosetting resin component builds onto the resin of the precastreinforcement 21 so that when the molded structure is' subjected to destructive loads the structure behaves as an integral body. I i

A mold useful in forming the reinforcing portion of the last heel end comprises a simple two-part'mold shown in Fig. 4. The cooperatingtparts 30 and 32 of the mold comprise shaped portions 34 and 36 and cooperating flat portions 38 and 40 which fit together to seal'the joint between the two parts of the' mold. A funnel shaped opening 42 is provided in the upper portion of the last mold for filling material into the mold after assembly of the two parts.

The shaped surface portions comprise central surfaces 44 for forming the web portion22 and a continuous channel 46 around the central surfaces44 to form tlie flange portions 24 and 28 of the reinforcement. Channels 48 are provided to receive a mold insert 50 to form the slot 16 for the hingelink. The insert 50 has a hole 52 and holes 54 are provided in the mold parts 30 and 32 to receive a pin 56 for forming a hole in the hinge pin support section to receive the hinge pin. The two mold parts are clamped together during molding by suitable means not shown.

A second simple two-part mold shown in Fig. 6 may be employed for forming the completed heel end. ..The parts 60 and 62 of the mold comprise surface portions 64 and 66 having a contour for shaping a heel end, and cooperating fiat portions 68 for forming a sealed joint between the two mold parts. A funnel-shaped opening 70 is provided in the upper portion of the mold for introduction of material into the mold after assembly of the two parts. Holes 72 are provided in the forward portion Y or the mold parts to receive a pin 74, and channels 75 are provided to receive the mold inserts 50. In use of the mold the reinforcement portion 21 of the last heel end 10 with the mold insert 50 in the slot 16 is placed in the cavity formed by the surface portions 64 and 66 of the last heel end mold parts 60 and 62 with theholes 54 and 55 in alinement with the holes 72 in the mold and the pin 74 is inserted through the hole 72 in one side of the last heel end mold, through the hinge pin receiving holes 23 in the reinforcement portion and hole 55 in the mold insert and through the hole 72 in the other mold part. With the reinforcement portion 21 thus secured in the last heel end mold, the top and bottom surfaces of the reinforcement portion 21 are in engagement with the portions of the mold surface which will form the top and bottom of the last heel end. Also, the reinforcement portion 21 is approximately centered with respect to the surface portions 64 and 66 of the molding surface and is held in this relation by the pin 74. For molding, the mold parts 60 and 62 are held together by suitable means not shown.

It is possible also to prepare a moldable but shaperetaining mixture of inorganic reinforcing filler and thermosetting resin, form this mixture to the shape of the desired reinforcement, place it in a last heel end mold, fill the remaining portions of the mold with the mixture of thermosetting resin and hollow resin spheres and cure the composite in a single stage.

For the continuous resin it is preferred to use thermosetting epoxy resins and polyester resins which are liquid in uncured form and set up on addition of a curing agent to a hard, strong, infusible mass. For example, resinous polyglycidyl polyethers of polyhydric phenols such as the materials commercially available as Epon resins or A'raldite resins have been found useful; and amine curing agents such as the commercially available Shell Curing Agent D may be used. Other thermosetting resins such as the thermosetting phenol-aldehyde resins may be used. Metallic aluminum powder is the preferred' inorganic reinforcing filler material because this mixture when cured is machinable to a smooth surfaced free-sliding body. Aluminum'powder 'of particle size capable of passing through a 100 to 200 mesh sieve is suitable. Other reinforcing fillers such as finely divided silicas and carbon black may be used. M i

.The following example is given to aid in understanding the invention but'it is to be understood that the invention is not restricted to the materials, proportions or pro cedure set forth in the example.

Example 1800 parts by weight of a normally liquid resinous glycidyl polyether of a polyhydric phenol having a melt ing' point of 8 to 12 C. and an epoxide equivalent of 190 to'2l0 (Epon 828) and parts by weight of allyl glycidyl ether were mixed in a ribbon type mixer to which were added 36 parts by weight of a cationic amine to improve the wetting of aluminous powder by tlie'resin. The amine employed 1-hydroxy ethyl, Z-heptade'ehyl glyoxalidine. Thereafter 3600 parts by weight" of mesh aluminum powder were added and thoroughly mixed in. Finally 240 parts by weight of an arninecuring agent were added and the mixture was stirred until uniform. The temperature of the mixture was raised to 70 C. to improve its fluidity, it was then poured into the reinforcement portion mold (see Fig. 4) which had been preheated to 70 C. and the mixture was cured in the mold for 2 /2 hrs. at this temperature. The molded reinforcement portion was then removed from the mold and positioned in a heel end mold (see Fig. 6) by means of a bolt extending through the holes in the walls of the mold and passing through the openings in the molded body.

parts by weight of liquid glycidyl polyether of a polyhydric phenol and 62.5 parts by weight of a molten glycidyl polyether of a polyhydric phenol (Epon 1001) having a melting point of 70 C. and an epoxide equivalent of 450 to 525 were mixed and the temperature was brought to about 80 C. When mixing was complete there were stirred in 62.5 parts by weight of liquid polysulfide polymer (Thiokol LP3) as a plasticizer and the mixture was then cooled to room temperature. This mixture was placed in an agitator and 3.75 parts by weight of a cationic wetting agent and 0.5 part by weight of a commercial silicone antifoam were added and mixed in. The mixture was then heated to 70 C. and 31.25 parts by weight of microscopic hollow spheres of phenolic resin were added and the mixture violently beaten to form a uniform dispersion. Thereafter 13.75 parts by weight of allyl glycidyl ether were added and thoroughly mixed in. An additional 31.25 parts by weight of the hollow resin spheres were added and mixed in. Finally 16.25 parts by weight of an amine curing agent were added and mixed until dispersed.

This mixture of resin and hollow resin spheres was introduced into the space between the walls of the heel end mold and the precast aluminum resin mixture. The filled mold was kept at a temperature of from 55 to 65 C. for 2 /2 hours to complete curing; and the molded resin article was then removed from the mold. The rough molded heel end was then turned to ultimate size on a standard wood last turning lathe. On testing the heel end in shoemaking, it was demonstrated that the heel end carried the loads of heeling, heel seat lasting, sole leveling and other shoemaking operations without permanent distortion or fracture. Thus no fracture or noticeable distortion occurred in over 500 cycles on a McKay automatic heel loading and attaching machine at maximum pressure of 14,500 lbs. Over 100 cycles in the sole leveling machine at maximum load likewise produced no permanent distortion. The heel end showed satisfactory nail and tack holding ability. The heel end is much less affected by humidity than is wood; thus when the heel end was assembled with a last forepart and held in storage for three weeks at 120 F. and high humidity, there was no observable dimensional change and no loss of spring tension at the hinge.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. A light, strong, dimensionally stable last heel end comprising a continuous phase of strong resin extending substantially throughout said heel end, solid particles of reinforcing inorganic filler dispersed in said continuous phase localized in a centrally disposed column and holloW resin spheres dispersed through the remainder of said continuous phase, said central column constituting a reinforcement including a portion surrounding openings for receiving a last hinge pin and a portion extending substantially from top to bottom of said last heel end and joined to said portion surrounding said openings to support the stresses exerted on the last hinge and other portions of the last heel end in shoemaking operations.

2. A light, strong, dimensionally stable last heel end comprising a continuous phase of strong thermoset resin extending substantially throughout said heel end, solid particles of reinforcing inorganic filler dispersed in said continuous phase localized in a centrally disposed column with portions of greater thickness disposed away from the neutral axis of said pattern and hollow resin spheres dispersed through the remainder of said continuous phase, said central column constituting a reinforcement including a portion surrounding openings for receiving a last hinge pin and a portion extending substantially from top to bottom of said last heel end and joined to said portion surrounding said openings to support the stresses exerted on the last hinge and other portions of the last heel end in shoemaking operations.

3. A light, strong, dimensionally stable last heel end formed of a continuous phase of strong thermoset resin extending substantially throughout said heel end, solid particles of reinforcing inorganic filler dispersed in said continuous phase localized in a pattern including a web extending substantially in the line of stress applied to said heel end and flange portions spaced from the neutral axis of said pattern and hollow resin spheres dispersed through the remainder of said continuous phase, said pattern including a portion surrounding openings for re ceiving a last hinge pin and a portion extending substantially from top to bottom of said last heel end and joined to said portion surrounding said openings to support the stresses exerted on the last hinge and other portions of the last heelend in shoemaking operations.

References Cited in the file of this patent UNITED STATES PATENTS 1,397,842 Netzel Nov. 22, 1921 

1. A LIGHT, STRONG, DIMENSIONALLY STABLE LAST HEEL END COMPRISING A CONTINUOUS PHASE OF STRONG RESIN EXTENDING SUBSTANTIALLY THROUGHOUT SAID HEEL END, SOLID PARTICLES OF REINFORCING INORGANIC FILLER DISPERSED IN SAID CONTINOUS PHASE LICALIZED IN A CENTRALLY DISPOSED COLUMN AND HOLLOW RESINS SPHERES DISPERSED THROUGH THE REMAINDER OF SAID CONTINUOUS PHASE, SAID CENTRAL COLUMN CONSTITUTING A REINFORCEMENT INCLUDING A PORTION SURROUNDING OPENINGS FOR RECEIVING A LAST HINGE PIN AND A PORTION EXTENDING SUBSTANTIALLY FROM TOP TO BOTTOM OF SAID LAST HEEL END AND JOINED TO SAID PORTION SURROUNDING SAID OPENINGS TO SUPPORT THE STRESES EXERTED ON THE LAST HINGE AND OTHER PORTIONS OF AT LAST HEEL END IN SHOEMAKING OPERATIONS. 